This is an extremely simple addon I made for doing rated BGs with my guild. All it does if an enemy mage drops a Ring of Frost it says [Enemy: {name} has dropped a Ring of Frost! Get out of it!] in [Say][Raid] and [Raid Warning] if possible. The only setback is you have to be in range for the combat log to pick it up, however the combat log works from pretty far, almost half the battle ground.
This addon only runs in battleground/arenas and has no configuration.